Table 2: Multivariable analysis with the ZTNB model. The best predictors’ model for number of deaths from RTAs.

  Unadjusted Estimates Adjusted Estimates
Variable IRR (95% CI) P-value IRR (95% CI) P-value
Driver’s age (years): 1.04 (1.03,1.05) <0.0001 1.01 (0.99, 1.03) 0.358
Driver’s sex: Female
Male		 Ref
4.92		   1
(1.07, 22.58)		   1
0.040		 Ref
9.57		   1
(0.96, 95.46)		   1
0.054a
Time:Night (7pm-12am)
Early morning (1-6am)
Morning (7am-12pm)
Afternoon (1pm-6pm) 		Ref
2.59
5.03
1.17		   1
(1.59, 4.24)
(3.26, 7.74)
(0.75, 1.84)		   1
<0.0001
<0.0001
0.489		 Ref
2.11
1.78
0.93		 1
(1.01, 4.41)
(0.91, 3.49)
(0.51, 1.70)		 1
0.048a
0.094
0.805
Vehicle type: Private
Public
Truck		 Ref
8.90
2.10		   1
(5.66, 13.98)
(1.37, 3.21)		   1
<0.0001
0.001		 Ref
5.65
2.19		 1
(2.97, 10.73)
(1.25, 3.82)		 1
< 0.0001a
< 0.0001a
“Cause” of accident:
Exces.speed/overtaking
Crossing road
Cutting in/FTKNS
Unlicensed/Inexperience
Hit&Run/Unknown
Stretch: Lusaka-Katuba
Katuba-Landless corner
Landless corner-ZNS
ZNS-Mul. Univ.
Mul. Univ.-K/mposhi 		 N/A
Ref
0.03
0.29
1.20
2.04
Ref
4.93
20.49
7.95
8.64		   N/A
  1
(0.01, 0.09)
(0.16, 0.51)
(0.41, 3.55)
(1.37, 3.04)
  1
(2.01, 12.10)
(9.57, 43.85)
(3.63, 17.38)
(4.15, 17.98)		   N/A
  1
< 0.0001
< 0.0001
0.738
< 0.0001
  1
< 0.0001
< 0.0001
< 0.0001
< 0.0001		 N/A
Ref
0.04
0.17
1.29
1.05
Ref
4.41
9.01
3.60
5.73		 N/A
  1
(0.01, 0.12)
(0.07, 0.42)
(0.35, 4.83)
(0.60, 1.85)
  1
(1.39,14.01)
(3.29, 24.62)
(1.33,9.74)
(2.23, 14.73)		 N/A
1
<0.0001a
<0.0001a
0.701
0.860
  1
0.012a
< 0.0001a
0.012a
< 0.0001a

aSignificant variables at 0.05 level of significance (Adjusted estimates), Ref: Reference/comparison group, IRR: Incident rate ratio, 95% CI: 95% Confidence Interval. FTKNS: Failure to keep near side, ZNS: Zambia National Service.